作为钠硫电池正极的碳约束NiS2纳米结构中钠离子的储运特性

Storage and Transport Properties of Sodium-ions of Carbon-constraint NiS2 Nanostructure as Cathode for Na-S Batteries

用电弧蒸发法和固相硫化法制备核壳结构的碳约束NiS2纳米材料(NiS2@C)。用X射线衍射(XRD)、透射电镜(TEM)和Raman等手段对其表征的结果表明,外部碳层有较多的缺陷,厚度为4 nm,NiS2的粒径为28 nm。作为Na-S电池正极材料的电化学性能:在电流密度为100 mA·g-1条件下NiS2@C正极材料4次循环后库伦效率保持在90%以上,循环500次后仍有106.8 mAh·g-1的可逆比容量,具有较高的循环稳定性。电化学阻抗分析结果表明,NiS2@C外部碳层的良好电子导电性和优异的结构稳定性加快了电极反应并维持着界面离子迁移的动力学平衡。

Carbon-constraint NiS2 nanomaterials(NiS2@C)with core-shell structure were successfully synthesized by a combination method of arc evaporation and solid-state vulcanization.Characterization results of X-ray diffraction(XRD),transmission electron microscopy(TEM)and Raman spectroscopy show that there existed rich defects in the carbon shell.The thickness of the carbon shell was 4 nm,and the diameter of the NiS2 core was 28 nm.The electrochemical performance of NiS2@C electrode was measured as the cathode materials for Na-S batteries.The Coulombic efficiency of NiS2@C electrode remained above 90%after four cycles at a current density of 100 mA·g-1,and the reversible specific capacity of 106.8 m Ah·g-1 remained after 500 cycles,which showed high cyclic stability.The electrochemical impedance analysis reveals that the electrode reactions were accelerated and the dynamic equilibrium of ion migration at the interface was maintained due to its good electronic conductivity and excellent structural stability by the constraint of the external carbon layer.